Synthetic woven and nonwoven fabrics are used to make a variety of products having various levels of softness, strength, durability, uniformity, liquid handling properties such as absorbency, liquid barrier properties, and other physical properties. Such products include towels, industrial wipes, incontinence products, infant care products such as baby diapers, absorbent feminine care products, and garments such as medical apparel. These products are often made with monolayer or multiple layer fabrics to obtain the desired combination of properties.
Woven and nonwoven fabrics are commonly made from fibers prepared by melt spinning thermoplastic materials, i.e., spunbond materials. Methods for making spunbond polymeric materials are well-known. Spunbond fibers are made by extruding a thermoplastic composition through a spinneret and drawing the extruded material into filaments with a stream of high velocity air. The filaments are then woven into fabrics or used to form a nonwoven fabric by forming a random fiber web on a collecting surface.
Spunbond materials with desirable combinations of physical properties, especially combinations of softness, strength and durability, have been produced, but limitations have been encountered. For example, for some applications, polymeric materials such as polypropylene may have a desirable level of strength but not a desirable level of softness. On the other hand, materials such as polyethylene may, in some cases, have a desirable level of softness but not a desirable level of strength. Accordingly, there is a need for fabrics that exhibit a balance of properties.
For fabrics that contact skin, such as the outer cover layer of a disposable baby diaper, it is desirable to improve the durability of nonwoven fabric while maintaining high levels of softness. Unfortunately, conventional nonwoven fabrics including a softer component, e.g., polyethylene, and a high strength component, e.g., polypropylene, have bonds between the multicomponent strands that are less durable and tend to pull apart when subjected to a load. Thus, more durable fabrics are needed.
Unfortunately, combinations of favorable properties are especially difficult to achieve for fine fibers due to the high spinning speeds needed to prepare such fibers. At higher spinning speeds, balanced properties are more difficult to achieve when using materials having tensile and elongational properties that are related to molecular weight, crystallinity, and molecular orientation of the fiber. In such applications, molecular orientation is relatively high, which results in low fiber orientation and fabrics that are not stretchable.
Accordingly there exists a current and long felt need for compositions that provide woven and/or nonwoven fabrics that overcome known deficiencies in conventional compositions, have advantageous processing and generally have enhanced levels of softness, durability, and elasticity.